There is airflow around a cartridge, but not through a cartridge. Juice is transferred by 'wicking' action when the cart filler comes in contact with the meshy material of the atomizer bridge. If the affinity of the smoking liquid to cling to the spun poly filling is greater than the wicking action, juice remains in the filling. Your
vaping habits can also have an effect on wicking. I find that a heavy vaping session does not allow juice enough time to wick to the atomizer bridge leaving the end very dry, very quickly.
The whole process is generally pretty simple, yet elegant. I would guess experimenting with alternative cart filling material would be a better way to go.